Acoustical sound proofing material and methods for manufacturing same

ABSTRACT

An improved acoustical damping wall (ceiling or floor) or door material comprises a laminar structure having as an integral part thereof one or more layers of viscoelastic material which also functions as a glue and one or more constraining layers, such as metal, cellulose, wood, or petroleum-based products such as plastic, vinyl, plastic or rubber. In one embodiment, standard wallboard, typically gypsum, comprises the external surfaces of the laminar structure; and one or more constraining layers are fabricated between the gypsum exterior. The resulting structure improves the attenuation of sound transmitted through the structure.

FIELD OF THE INVENTION

This invention relates to acoustical damping materials and, inparticular, to soundproofing materials of a novel laminar constructionwhich significantly improves the soundproofing ability of walls,ceilings, floors, and doors, thereby to prevent the transmission ofsounds from one area to another.

BACKGROUND OF THE INVENTION

Noise is emerging as both an economic and public policy issue.Soundproof rooms are required for a variety of purposes. For example,apartments, hotels and schools all require rooms with walls, ceilingsand floors that minimize the transmission of sound thereby to avoidannoying people in adjacent rooms. Soundproofing is particularlyimportant in buildings adjacent to public transportation, such ashighways, airports and railroad lines, as well as theaters, hometheaters, music practice rooms, recording studios and others. Onemeasure of the severity of the problem is the widespread emergence ofcity building ordinances that specify minimum Sound Transmission Class(“STC”) rating. Another measure is the broad emergence of litigationbetween homeowners and builders over the issue of unacceptable noise. Tothe detriment of the U.S. economy, both problems have resulted in majorbuilders refusing to build homes, condos and apartments in certainmunicipalities; and in widespread cancellation of liability insurancefor builders.

In the past, walls typically were made up of studs with drywall on bothexterior surfaces of the studs and baffles or plates commonly placedbetween the studs in an attempt to reduce the transmission of sound fromone room to the next. Unfortunately, even the best of such walls usingstandard drywall are capable of only reducing sound transmission byapproximately 30 db, and much of that is focused on mid-range and highfrequencies rather than lower frequencies which cause most of thecomplaints and litigation.

Various techniques and products have emerged to abate this problem, suchas: replacement of wooden studs by steel studs; resilient channels tooffset and isolate drywall panels from studs; mass-loaded vinylbarriers; cellulose sound-board; cellulose and fiberglass battinsulation; and techniques such as staggered-beam and double-beamconstruction. All help reduce the transmission of noise, but, again, notto such an extent that certain sounds (e.g., lower frequencies, highdecibel) in a given room are prevented from being transmitted to anadjacent room, including rooms above or below. A brief review ofcommercially available products shows that there has been littleinnovation in these techniques and technologies for many years.

Accordingly, what is needed is a new material and a new method ofconstruction to reduce the transmission of sound from a given room to anadjacent room.

SUMMARY OF THE INVENTION

In accordance with this invention a new laminar and associatedmanufacturing process is provided which significantly improves theability of a wall, ceiling, floor or door to reduce the transmission ofsound from one room to an adjacent room, or from the exterior to theinterior of a room, or from the interior to the exterior of a room

The material comprises a lamination of several different materials. Inaccordance with one embodiment, a laminar substitute for drywallcomprises a sandwich of two outer layers of selected thickness gypsumboard which are glued each to an interior constraining layer, such as ametal, cellulose (e.g., wood) or petroleum-based product such as vinyl,composite plastic or rubber, using a sound absorbent adhesive. In oneembodiment, the constraining layer comprises a selected thicknessgalvanized steel and the glue layer is a specially formulated QuietGlueof a specific thickness which is a viscoelastic material. Formed on theinterior surfaces of the two gypsum boards, the glue layers are eachabout {fraction (1/16)} inch thick and the galvanized steel between0.005 and 0.5 inch thick. In one instance, a 4 foot×8 foot panelconstructed using a {fraction (1/16)}″ layer of glue and 30 gaugegalvanized steel weighs approximately 108 pounds versus the weight of atypical drywall of the same thickness of about 75 pounds, has a totalthickness of approximately ⅝ inches and has an STC of approximately 38.The double-sided standard construction using this particular materialwill give an STC of approximately 58. The result is a reduction in noisetransmitted through the wall of approximately 60 db compared to a 30 dbreduction of transmitted noise using standard commercially availabledrywall.

In one embodiment, the galvanized steel metal layer is preferably notoiled and of regular spackle. The resulting product, even though itcontains the galvanized steel center sheet, can be cut with a standardhand saw using wood blades, but cannot be scribed and broken likeordinary drywall.

Another embodiment of this invention uses additional layers of materialand is non-symmetric. Two external gypsum board layers have directlyadjacent their faces layers of quiet glue, followed by two metal layers,followed by two additional layers of glue, and then a central piece oflaminated wood (in one embodiment a layer of laminated wood of the typeused in plywood). The total finished thickness of this structure canvary, but the additional two layers of metal result in a significantincrease in the attenuation of sound passing through the material.

The laminated sheets of this invention use unique glues capable ofsubstantially absorbing sound and vibration together with one or moreconstraining layers which reduce the transmissibility of the sound fromone layer to the adjacent layers of material. The constraining layerscan be metal, cellulose, wood, plastic composites, vinyl or other porousor semi-porous materials. The resulting attenuation of sound issignificantly improved compared to the attenuation of sound obtainedusing standard drywall.

DETAILED DESCRIPTION OF THE DRAWINGS

This invention will be more fully understood in light of the followingdrawings taken together with the following detailed description.

FIG. 1 shows a laminar structure fabricated in accordance with thisinvention for reducing the transmission of sound through the material.

FIG. 2 shows a second embodiment of a laminated structure containingnine (9) layers of material capable of significantly reducing thetransmission of sound through the material.

FIGS. 3 and 4 show alternative embodiments of this invention capable ofreducing the transmission of sound through the material.

FIGS. 5-10 show sound attenuation test results on several embodiments ofthis invention.

DETAILED DESCRIPTION

The following detailed description is meant to be exemplary only and notlimiting. Other embodiments of this invention—such as the number, type,thickness and placement order of both external and internal layermaterials—will be obvious to those skilled in the art in view of thisdescription.

The process for creating such laminar panels takes into account manyfactors: exact chemical composition of the glue; various symmetric andnon-symmetric thicknesses of glue and layered material; pressingprocess; drying and dehumidification process.

FIG. 1 shows the laminar structure of one embodiment of this invention.In FIG. 1, the layers in the structure will be described from top tobottom with the structure oriented horizontally as shown. It should beunderstood, however, that the laminar structure of this invention willbe oriented vertically when placed on vertical walls and doors, as wellas horizontally or even at an angle when placed on ceilings and floors.Therefore, the reference to top and bottom layers is to be understood torefer only to these layers as oriented in FIG. 1 and not in the contextof the vertical use of this structure. In FIG. 1, the top layer 11 ismade up of a standard gypsum material and in one embodiment is ¼ inchthick. Of course, many other combinations and thicknesses can be usedfor any of the layers as desired. The thicknesses are limited only bythe acoustical attenuation (i.e., STC rating) desired for the resultinglaminar structure and by the weight of the resulting structure whichwill limit the ability of workers to install the laminar layer on walls,ceilings, floors and doors for its intended use.

The gypsum board in top layer 11 typically is fabricated using standardwell-known techniques and thus the method for fabricating the gypsumboard will not be described. Next, on the bottom of the gypsum board 11is a layer of glue 12 called “QGquiet glue™”. Glue 12, made of a uniqueviscoelastic polymer, has the property that the energy in the soundwhich strikes the glue, when constrained by surrounding layers, will besignificantly absorbed by the glue thereby reducing the sound'samplitude across a broad frequency spectrum, and thus the energy ofsound which will transmit through the resulting laminar structure.Typically, this glue is made of the materials as set forth in TABLE 1,although other glues having the characteristics set forth directly belowTable 1 can also be used in this invention. TABLE 1 Quiet Glue ™Chemical Makeup WEIGHT % Components Min Max acetaldehyde 0.00001%0.00010% acrylate polymer 33.00000%

acrylonitrile 0.00001% 0.00100% ammonia 0.00100% 0.01000%bis(1-hydroxy-2-pyridinethionato) Zinc 0.01000% 0.10000% butyl acrylate0.00100% 0.10000% butyl acrylate, methyl methacrylate, 5.00000%15.00000% styrene, methacrylic acid 2- hydroxyethyl acrylate polymer CIPigment Yellow 14 0.01000% 0.02000% ethyl acrylate 0.00001% 0.00010%ethyl acrylate, methacrylic acid, 1.00000% 5.00000% polymer withethyl-2-propenoate formaldehyde 0.00100% 0.01000% hydrophobic silica0.00100% 0.01000% paraffin oil 0.10000% 1.00000% polymeric dispersant0.00100% 0.01000% potassium tripolyphosphate 0.00000% 0.00200% silicondioxide 0.00100% 0.10000% sodium carbonate 0.01000% 0.10000% stearicacid, aluminum salt 0.00100% 0.10000% surfactant 0.00100% 0.10000% vinylacetate 0.10000% 1.00000% water 25.00000% 40.00000% zinc compound0.00100% 0.10000%The physical solid-state characteristics of QuietGlue include:

1) a broad glass transition temperature below room temperature;

2) mechanical response typical of a rubber (i.e., high elongation atbreak, low elastic modulus);

3) strong peel strength at room temperature;

4) weak shear strength at room temperature;

5) swell in organic solvents (e.g., Tetrahydrofuran, Methanol);

6) does not dissolve in water (swells poorly);

7) peels off the substrate easily at temperature of dry ice.

Following glue layer 12 is a metal layer 13. Metal layer 13 is, in oneembodiment, 30 gauge galvanized steel of 0.013 inch thickness. Ofcourse, other gauge galvanized steel and even other metals can be usedif desired. For example, aluminum can also be used if desired, as canspecialty metals such as sheets of ultra-light weight titanium andlaminated layers of metal including laminates of aluminum and titanium.Of importance is that galvanized steel, if used, be non-oiled and ofregular spackle. Non-oil is required to insure that the QuietGlue layer12 will adhere to the top surface of metal layer 13 and the adjacentQuietGlue layer 14 on the bottom of metal layer 13 will also adhere tothe surfaced metal 13. Regular spackle insures that the metal hasuniform properties over its whole area.

Next, glue layer 14 is placed in a carefully controlled manner withrespect to coverage and thickness on the bottom of metal layer 13. Gluelayer 14 is again a viscoelastic material which absorbs sound and istypically the same material as glue layer 12. Finally, gypsum boardlayer 15 is placed on the bottom of the structure and carefully pressedin a controlled manner with respect to uniform pressure (pound persquare inch), temperature and time

Finally, the assembly is subjected to dehumidification and drying toallow the panels to dry, typically for forty-eight (48) hours.

Typically, but not always, gypsum board layers 11 and 15 will containfiber to reduce shrinkage so that the resulting laminar structure willmeet fire codes. Typical fire codes require a wall structure capable ofwithstanding flames for up to one hour. The metal core, together withthe external gypsum board layers are intended to give to the resultinglaminar structure a minimum of one hour resistance to fire, and possiblyas high as four (4) hours in certain configurations, and thereby allowsthe resulting structure to meet typical fire codes.

Metal layer 13, typically 30-gauge steel (but may be other metals,ranging from 10 gauge to 40 gauge, depending on weight, thickness, andSTC desired), is about the thickness of a business card. Of importance,before assembling, this metal should not be creased because creasingwill ruin the ability of this metal to assist in reducing thetransmission of sound. Only completely flat, undamaged pieces of metalcan be used in the laminar structure.

In an alternative embodiment, steel 13 is replaced by mass-loaded vinylor similar product. However, the steel has much less forgiveness thanvinyl and thus can outperform vinyl as a constraining layer. However,for other ease-of-cutting reasons, vinyl can be used in the laminarstructure in place of steel, if desired. Cellulose, wood, gypsum,plastic or other constraining materials may also be used in place ofvinyl or metal. The alternative material can be any type and anyappropriate thickness.

The resulting structure is capable of being cut using standard wood sawswith wood blades.

FIG. 2 shows a second embodiment of this invention. Two external layers21 and 29 of gypsum board have coated on each of their interior faces alayer of QuietGlue 22 and 28, respectively, preferably made of aviscoelastic polymer, such as glue 12 in FIG. 1. Such a viscoelasticpolymer has the ability to absorb sound energy through deformation ofthe viscoelastic material in response to the acoustic energy of thesound. On the interior faces of the QuietGlue are two sheet metal layers23 and 27. Typically, these sheet metal layers 23 and 27 are eachgalvanized steel. In one embodiment, the galvanized steel is 30 gauge,0.013 inches thick, but other thicknesses of steel, as well as othermetals, can also be used as desired. The interior faces of the steellayers 23 and 27 are coated with additional layers 24 and 26,respectively, of quiet glue, again a viscoelastic material of the sametype as glue layers 22 and 28. Then the core of the structure is made upof a pine laminar sheet 25 which is of a type commonly used in plywood.In one embodiment, the pine laminar sheet is {fraction (1/10)}^(th) ofan inch thick, but may also be MDF or other wood types.

Again, the galvanized steel is non-oiled and regular spackle for thereasons discussed above in conjunction with the embodiment of FIG. 1.The layers of glue are all viscoelastic material capable of absorbingsound. The resulting product has a thickness of approximately ⅞^(th) ofan inch and weighs approximately 148 pounds per 4×8 section. Thestand-alone STC for the resulting material is 42 which yields adouble-sided standard construction STC of 62. The steel layers shouldnot be creased before assembly. Creasing of the steel may ruin the steelfor its intended purpose. Using completely flat pieces undamaged isrequired to achieve optimal results. The resulting structure again iscutable with a standard power saw using wood blades. The interior layer25 of wood is in one embodiment Sierra pine {fraction (1/10)}^(th) inchthick MDF acquired in Rocklin, Calif. (http://www.sierrapine.com).

In fabricating the structures of FIGS. 1 and 2, the glue is first rolledin a prescribed manner, typically to {fraction (1/16)} inch thickness,although other thicknesses can be used if desired, onto the gypsum andthen steel is laid on the glue. Depending on the drying anddehumidification techniques deployed, anywhere from 10 to 30 hours arerequired to dry totally the glue in the case that the glue iswater-based. A solvent-based viscoelastic glue can be substituted. Theresulting structure is dried in a prescribed manner under a pressure ofapproximately 2 to 5 pounds per square inch, depending on the exactrequirements of each assembly, although other pressures can be used asdesired. To make the embodiment of FIG. 2, each of the gypsumboard-glue-metal layer structures has an additional layer of glue rolledonto the exposed surface of the metal to approximately {fraction(1/16)}^(th) inch thickness and then the thin pine wood layer is placedbetween the two layers of glue on the already fabricatedgypsum-glue-metal sheets. The resulting structure is placed in a pressand 1 to 5 pounds per square inch of pressure is applied to thestructure and up to 48 hours is allowed for drying.

FIG. 3 shows another embodiment of the acoustical soundproofing materialof this invention. In FIG. 3, two external layers of gypsum board 30 and34 have on their interior faces glue layers 31 and 33, respectively.Between the two glue layers 31 and 33 is a constraining material 32 madeup of vinyl. This vinyl is mass loaded and, in one embodiment, is 1pound per square foot or greater, and is available from a number ofmanufacturers, including Technifoam, Minneapolis, Minn. The total weightof this structure when the external layers 30 and 34 of gypsum board areeach ⅝ inch thick, the layers of viscoelastic QuietGlue 31 and 33 areeach approximately {fraction (1/16)} of an inch thick and the massloaded vinyl is approximately {fraction (1/32)} of an inch thick, isabout 190 pounds per 4×8 foot section. The total finished thickness ofthe material is 1.3 to 1.5 inches depending on the thickness of thevinyl and the actual thicknesses of the viscoelastic QuietGlue layers 31and 33.

The embodiment of FIG. 3 cannot be scored like regular drywall, butrather must be cut using a wood saw. A typical wood saw blade isadequate to actually cut the soundproofing material of FIG. 3.

FIG. 4 shows an additional embodiment of the soundproofing material ofthis invention. In this embodiment, two external layers 35 and 39 are ⅝inch plywood and have on their interior faces layers 36 and 38 of quietglue, respectively. Between the QuietGlue is a layer of mass loadedvinyl 37. The structure shown in FIG. 4 is meant to be used on floors orin other construction areas where wood would normally be used. Theplywood sheets 35 and 39 are each typically ⅝ inch thick in oneembodiment. In this embodiment, the layers of QuietGlue 36 and 38 areeach approximately {fraction (1/16)} inch thick (although otherthicknesses can be used if desired) and the mass loaded vinyl 37 istypically {fraction (1/16)} to ¼ inch thick. When the mass loaded vinylis ⅛ inch thick, then the total thickness of the structure of FIG. 4 isapproximately 1.5 inches thick. If the vinyl is {fraction (1/16)} inchthick, then the total thickness is approximately 1.4 inches.

The structure of FIG. 3 standing alone has an STC of 38, while thestructure of FIG. 4 has an STC of 36. The structures of FIGS. 1 and 2have STCs of 37 and 38, respectively.

It is noted that uneven application of QuietGlue or leaving an air gapat the ends of the sheets of soundproofing material described above mayhurt the STC ratings by several db. Moreover, to improve thesoundproofing qualities of walls, floors, ceilings or doors made withthese materials, glue must be evenly applied all the way to the ends andcorners of the sheets. None of the panels described above can be scoredlike regular drywall. Rather, these panels must be cut using a sawblade, typically a wood saw blade.

The sound transmission class numbers given above basically are numberswhich are used in the architectural field to rate partitions, doors andwindows for their effectiveness in blocking sound. The number assignedto a particular partition design as a result of STC testing represents abest fit type of approach to a set of curves that define the soundtransmission class. The test is conducted in such a way to make itindependent of the test environment and gives a number for the partitiononly. The STC measurement method is defined by ASTM E90 laboratory testfor sound measurements obtained in ⅓ octave bands, and ASTM E413 forcalculating “STC” (Sound Transmission Class) numbers from the soundtransmission loss in each partition, and these standards are availableon the internet at http://www.astm.org.

Data showing the transmission loss in decibels as a function offrequency for the soundproofing material of this invention is set forthin FIGS. 5, 6, 7, 8, 9 and 10. FIG. 5 shows a standard 2×4 constructionwith Quiet Rock Ultra, as shown in FIG. 3, on both sides of studs withno insulation. The transmission loss in decibels varies from 25 db at 63Hz to approximately 58 db at 4,000 Hz.

The center frequency of octave bands is set forth in the two rows of thetable. The top line of each row represents the ⅓ octave band centerfrequency. The second row of numbers in each horizontal categoryrepresents the total in db, and the third set of numbers represents a95% confidence level in db deficiencies. The EWR and OITC stand forExternal Wall Rating and Outdoor-Indoor Transmission Class,respectively, and represent other methods of measuring transmissionloss. The final sound transmission class number is set forth under thenotation STC in the lower right corner. For the use of two panels of thetype shown in FIG. 3, on both sides of standard 2″×4″ wood studconstruction, the STC is 54.

It is known to those practicing in this field that a similarconfiguration with standard ⅝ inch drywall on both sides of standard 2×4construction yields an STC of 34. Accordingly, this invention yields a20 STC point improvement over standard drywall in this particularconstruction.

The National Research Council of Canada (NRC) has documented the STCrating of many other configurations (e.g., using wood and steel studs instandard, staggered beam or double beam construction with variousisolators such as resilient channels and with various acousticinsulation fillers such as sound board, cellulose and fiberglass batt).This invention has been subjected to the same types of tests.

The use of a single panel, alone, of the type shown in FIG. 3 yields anSTC of 38, as shown in the bottom right corner of FIG. 6. Thus, the useof the single panel of the type shown in FIG. 1 to reduce soundtransmission is less effective than the use of two panels on both sidesof 2×4 studs as shown in FIG. 5.

The use of the structure shown in FIG. 4 on both sides of standard 2×4construction results in an STC of 49, as shown in FIG. 7. This indicatesthat the wood structure shown in FIG. 4 is less effective in reducingsound transmission than the structure shown in FIG. 3, which containsgypsum board on the external surfaces together with an internal layer ofvinyl, though both are significant improvements over standard materials.

FIG. 8 shows that the use of the wood structure in FIG. 4 on 2×4 studsalone, with no insulation, has an STC of 49, which is lower than the STCrating given to the structure of FIG. 3 in a similar configuration. Itis known to those practicing in this field that a similar wall withstandard plywood on both sides yields an STC rating of 29. Thus, thisrepresents a significant improvement over standard wood.

The use of the structure of FIG. 4 on one side with no insulation withstandard 2×4 construction results in an STC of 43, as shown in the graphof FIG. 9. This is a substantial improvement in sound attenuation overstandard plywood, but not as good as use of standard 2×4 constructionwith the structure of FIG. 4 on both sides of the studs, as shown inFIG. 85. Finally, the use of the structure of FIG. 4 alone results in anSTC of 36 as shown in FIG. 10, which is below the STC of 38 (FIG. 6) forthe structure of FIG. 3 in a similar configuration.

Accordingly, the laminar structure of this invention provides asignificant improvement in the sound transmission class numberassociated with the structures and thus reduces significantly the soundtransmitted from one room to adjacent rooms.

An alternative embodiment of this invention is asymmetric, being made upof a relatively thick layer of material on one surface of which isplaced viscoelastic glue. Over the viscoelastic glue is placed a thinlayer of material relative to the first layer of material. This thinlayer of material can be a constraining layer, such as metal or vinyl orrubber or any other appropriate thin material. This structure has soundreducing qualities, but is lighter and easier to handle than thestructures described in FIGS. 1 through 4. Such a structure, forexample, could be made up of layers 11, 12 and 13 of the structure shownin FIG. 1.

The dimensions given for each material in the laminar structures of thisinvention can be varied as desired to control cost, overall thickness,weight and STC results. The described embodiments and their dimensionsare illustrative only and not limiting.

Other embodiments of this invention will be obvious in view of the abovedescription.

1. A laminar structure used for constructing walls, floors, or ceilingsor doors comprising: two external layers of a material, at least oneinternal constraining layer, and two or more internal layers of aviscoelastic glue separated by said at least one internal constraininglayer.
 2. Structure as in claim 1, wherein the constraining layercomprises metal.
 3. Structure as in claim 1, wherein said two externallayers comprise each a selected thickness gypsum board layer. 4.Structure as in claim 3, wherein said glue comprises a viscoelasticmaterial capable of absorbing sound.
 5. Structure as in claim 4, whereinsaid internal metal layer comprises a sheet metal layer of selectedthickness.
 6. Structure as in claim 5, wherein said sheet metal layer ofselected thickness comprises galvanized steel.
 7. A laminar structurecomprising: at least one internal layer of a selected material; twointernal layers of a viscoelastic glue, one such layer on each side ofsaid internal layer; and at least one additional layer on the other sideof each internal layer of viscoelastic glue.
 8. Structure as in claim 7wherein said at least one additional layer comprises an external layerof a first sound absorbing material.
 9. Structure as in claim 8 whereinsaid external layer of a first sound absorbing material comprisesgypsum.
 10. Structure as in claim 8 wherein said at least one externallayer comprises a plurality of layers of selected materials. 11.Structure as in claim 10 wherein said plurality of layers of selectedmaterials comprise: a first layer of metal; a second layer ofviscoelastic glue; and a third layer of selected material.
 12. Structureas in claim 11 wherein said third layer of selected material comprisesgypsum.
 13. Structure as in claim 7 wherein said at least one internallayer comprises a metal layer.
 14. Structures in claim 7 wherein said atleast one internal layer comprises a layer of a cellulose material suchas wood.
 15. Structures in claim wherein said at least one internallayer comprises a layer of a solid petroleum-based synthetic materialsuch as a vinyl, plastic composite, or rubber.
 16. The method of forminga laminar structure which comprises: providing a layer of first materialhaving two surfaces; placing a layer of viscoelastic glue onto onesurface of said layer of first material; placing a layer of a secondmaterial over said viscoelastic glue; pressing said layer of secondmaterial against said layer of viscoelastic glue and said layer of firstmaterial for a selected time; and drying said layer of second material,said layer of first material and said viscoelastic glue.
 17. The methodof claim 16, including: providing an internal layer of material ormultiple layers of selected materials; forming a layer of viscoelasticglue on each of what are to be internal surfaces of two or more laminarstructures formed using the steps of claim 16; placing two or more suchlaminar structures with the two or more to-be internal surfaces adjacentsaid internal layer or said multiple layers; pressing the compositestructure formed in the preceding step at a selected pressure for aselected time; and drying the composite structure being pressed.
 18. Themethod of claim 16 wherein said first material comprises a metal layer,and said second material comprises a gypsum layer.
 19. The method ofclaim 17 wherein said internal layer comprises a cellulose-based layersuch as any wood.
 20. The method of claim 17 wherein said celluloselayer is wood.
 21. The method of claim 17 wherein said internal layercomprises a layer selected from the group consisting of vinyl, plasticcomposite, and rubber.
 22. The method of claim 18 wherein said internallayer comprises a metal layer selected from the group consisting ofgalvanized steel, stainless steel, aluminum, titanium, and a compositeof two or more metals.
 23. The method of claim 22 wherein said metallayer comprises galvanized steel.
 24. Structure as in claim 1 whereinthe internal constraining layer is a cellulose product, such as wood.25. Structure as in claim 24 wherein said cellulose product is wood. 26.Structure as in claim 1 wherein said at least one internal constraininglayer is selected from the group consisting of cellulose, wood, metal,plastic, vinyl, plastic composite and rubber.
 27. The method of forminga laminar structure which comprises: providing a layer of first materialhaving two surfaces; placing a layer of viscoelastic glue onto onesurface of said layer of first material; placing a layer of a secondmaterial, which is {fraction (1/100)}^(th) to ½ the thickness of thefirst material over said viscoelastic glue; pressing said layer ofsecond material against said layer of viscoelastic glue and said firstmaterial for a selected time; and drying said layer of second material,said layer of first material and said viscoelastic glue.
 28. The methodof claim 27 wherein said first material comprises a gypsum layer, andsaid second material comprises a metal layer.
 29. The method of claim 27wherein said first material comprises a gypsum layer, and said secondmaterial comprises a layer selected from the group consisting of plasticand a plastic composite layer.
 30. The method of claim 27 wherein saidfirst material comprises a gypsum layer, and said second materialcomprises a layer selected from the group consisting of vinyl andrubber.
 31. The method of claim 27 wherein said first material comprisesa gypsum layer, and said second material comprises a layer selected fromthe group consisting of cellulose-based material and wood.
 32. Themethod of claim 27 wherein said first material comprises a layerselected from the group consisting of a cellulose-based material andwood, and said second material comprises a metal.
 33. The method ofclaim 27 wherein said first material comprises a material selected fromthe group consisting of a cellulose-based material and a wood layer, andsaid second material comprises a material selected from the group ofmaterials consisting of a petroleum-based plastic composite and apetroleum-based rubber layer.
 34. The method of claim 27 wherein saidfirst material comprises a layer selected from the group consisting of acellulose-based material and wood, and said second material comprises alayer selected from the group consisting of a petroleum-based plasticcomposite, vinyl and rubber.
 35. The method of forming a laminarstructure which comprises: providing a layer of first material havingtwo surfaces; placing a layer of viscoelastic glue onto one surface ofsaid layer of first material; placing a layer of a second material oversaid viscoelastic glue; pressing said layer of second material againstsaid layer of viscoelastic glue and said first material for a selectedtime; and drying said layer of second material, said layer of firstmaterial and said viscoelastic glue.
 36. The method of claim 35 whereinthe two exterior layers are symmetric, made of the exact same type ofmaterial, and having the exact same density and thickness.
 37. Themethod of claim 35 wherein the two exterior layers are non-symmetric,made of other than the exact same type of material, and having otherthan the exact same density and thickness.
 38. The method of claim 35wherein the two or more interior layers are symmetric, made of the sametype of material, and having the same density and thickness.
 39. Themethod of claim 35 wherein the two or more interior layers arenon-symmetric, made of other than the exact same type of material, andhaving other than the same density and thickness.
 40. A laminar,sound-absorbing structure which comprises: a layer of first materialhaving two surfaces; a layer of viscoelastic glue on one surface of saidlayer of first material; and a layer of a second material over saidviscoelastic glue.
 41. A laminar, sound-absorbing structure as in claim40 wherein said layer of second materials is {fraction (1/10)}^(th) to ½the thickness of the first material.